Exiting the off-ramp in Truckee, CA., I looked up to the west at Donner summit. A place I climb frequently. There, covering 1/3 of place we call rock garden, that is, blocking out 1/3 of it was avery large,bright,white,shimmering, circular shaped object. By scale, aproximately 4-500 ft. in circumferance. It moved north to south at a very slow rate of speed. By the time we exited, went under the over-pass, and looked up again, it had moved approx. 5-600 yds. to the south. This was way too big to be any conventional aircraft, moved way too slow, and was too close to the peak. which was a great reference for me to scale the craft, since I had climbed there often. My friend also saw it briefly and took great interest. He later found there to be 4 other similar sightings in a 30 mile radius....that day. 1st report, 2nd sighting